1. Field of the Invention
The present invention relates to a rotational state detecting device, a lens device, and an optical apparatus.
2. Description of the Related Art
A video camera and a digital camera each have a manual operation ring for providing a drive instruction to a drive unit in a zooming optical system or a focusing optical system. Rotational states such as a rotational amount and a rotational direction when operating the operation ring are detected by a rotational state detecting device. An example of such a rotational state detecting device is a device using photo-interrupters or encoders.
FIG. 5 shows a conventional optical type rotational state detecting device using photo-interrupters.
Referring to FIG. 5, reference numeral 19 denotes an operation ring such as a manual operation ring. The operation ring 19 has a slit disk 19a integrally provided on the inner peripheral side thereof. The slit disk 19a has many slits radially formed. When the operation ring 19 is rotationally operated, the slit disk 19a also rotates integrally therewith. By this rotation, the slits of the slit disk 19a are detected (i.e., a transmitting state and a blocked state of a detecting light are detected) by photo-interrupters 20, and counting is performed. Thereby, the rotational amount of the operation ring 19 is detected. The purpose of providing two photo-interrupters as shown in FIG. 5 is to detect the rotational direction of the operation ring 19. Thus, by detecting slits of the slit disk 19a by the two photo-interrupters 20, rotational states such as a rotational amount and a rotational direction, of the operation ring 19 are detected, and the detected signals are outputted from the photo-interrupters.
Another example of a device for detecting a rotational state of an operation ring is a rotational state detecting device using MR sensors (magnetoresistive effect elements).
FIG. 6 shows a conventional magnetic type rotational state detecting device using an MR sensor.
As shown in FIG. 6, at the inner diameter portion of the operation ring 19, a magnetic scale 21, on which mutually different magnetic poles are alternately formed, is integrally provided. Reference numeral 22 denotes an MR sensor. The MR sensor 22 is spaced apart from the magnetized surface of the magnetic scale 21 by a predetermined distance. As the operation ring 19 is rotationally operated, the magnetic scale 21 also integrally rotates. Based on this rotation, the change of each of the magnetic poles in the magnetic scale 21 is detected by the MS sensor 22, and the detection signals are outputted from the MR sensor.
As described above, when manually operating a zooming optical system or a focusing optical system in an optical system such as a lens device, a video camera, or a digital still camera, the rotational state of the operation ring is detected by an optical or magnetic type rotational state detecting device, and the zooming optical system or the focusing optical system is caused to operate in response to the output signals as a result of the detection.
In recent lens devices and optical apparatuses (e.g., video cameras, digital still cameras), as the miniaturization of the apparatuses progresses, attempts to reduce the size of optical systems (e.g., lens devices) are also being made. In order to miniaturize an optical system, it is necessary to improve the resolution of the stop position of a scaling (zooming) optical system and a focusing optical system, and hence, it is necessary to improve detection resolution for the rotational states of the operation rings for manually operating zooming and focusing.
In the above-described optical type rotational state detecting device, the resolution for the rotational position of the operation ring is determined by the pitch of the slits formed on the slit plate. It is, therefore, necessary to reduce the pitch size of the slits. However, it is difficult to make the pitch size smaller than the current conditions because of the limitations of machining. This constitutes a problem in that for the conventional optical type rotational state detecting device it is difficult to improve the resolution over the current conditions.
On the other hand, in the conventional magnetic type rotational state detecting device, the rotational mechanism portion of the operation ring requires a certain level of clearance. Therefore, when the operation ring is rotated, the distance between the magnetic scale integrally provided on the operation ring and the MR sensor may change. Due to this change in distance, the output signal from the MR sensor may fluctuate. This raises a problem in that the correct rotational state of the operation ring cannot be detected.
Accordingly, it is an object of the present invention to solve the above-described problems, and provide a rotational state detecting device, a lens device, and an optical apparatus that are capable of correctly detecting the rotational states of operation rings, and that allow the miniaturization of the apparatus.
To achieve the above-described object, a rotational state detecting device according to the present invention includes operation rings each provided so as to be rotatable about a first axis, the operation rings each being rotated by external operation; support shafts provided so as to be rotatable about a second axis different from the first axis; disk-shaped scales each supported by a respective one of the support shafts; sensors each detecting the rotation of a respective one of the scales; and rotation transmitting mechanisms for respectively transmitting the rotation of each of the operation rings to a respective one of the support shafts.
A lens device according to the present invention includes a fixed cylinder having an optical axis; a lens unit moving in the direction of the optical axis of the fixed cylinder; operation rings each provided so as to be rotatable about the optical axis of the fixed cylinder, the operation rings each being rotated by external operation; support shafts each provided so as to be rotatable about an axis parallel to the optical axis; disk-shaped scales each supported by a respective one of the support shafts; sensors each detecting the rotation of a respective one of the scales; and rotation transmitting mechanisms for respectively transmitting the rotation of each of the operation rings to a respective one of the support shafts.
An optical apparatus according to the present invention, comprising a photographing optical system and an image pickup device that picks up images formed by the photographing optical system, includes a fixed cylinder having an optical axis; lens units moving in the direction of the optical axis of the fixed cylinder; actuators each driving a respective one of the lens units; operation rings each provided so as to be rotatable about the optical axis of the fixed cylinder, the operation rings each being rotated by external operation; support shafts each provided so as to be rotatable about an axis parallel to the optical axis; disk-shaped scales each supported by a respective one of the support shafts; sensors each detecting the rotation of a respective one of the scales; rotation transmitting mechanisms for respectively transmitting the rotation of each of the operation rings to a respective one of the support shafts; and controllers each controlling the driving of a respective one of the actuators in response to an output from a corresponding one of the sensors.
In another aspect, the present invention relates to a device comprising (a) a manual operation ring rotatable about an optical axis of the apparatus; (b) a support shaft rotatable about an axis parallel to the optical axis; (c) a disk-shaped scale supported by the support shaft; (d) a rotation transmitting mechanism that is configured to transmit the rotation of the manual operation ring to the support shaft; and (e) a sensor configured to detect the rotation of the disk-shaped scale.
In yet another aspect, the present invention relates to a device comprising (a) means for coupling a manual operation ring on a lens device to a magnetic scale having a diameter smaller than the manual operation ring so that rotation of the manual operation ring causes rotation of the magnetic scale; and (b) means for detecting rotation of the magnetic scale.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.